Treating waste water from a manhole or equipment vault is considerably more complex than treating an industrial waste water stream. In an industrial waste water stream, the contaminants in the water are usually constant and, once ascertained, a specific treatment process aimed at those contaminants can be implemented.
In contrast, contaminants in waste water from a manhole or equipment vault are varied in type and concentrations requiring treatment aimed at a multiplicity of contaminants. Furthermore, while industrial streams can implement permanent treatment facilities, treatment equipment for manholes and equipment vaults must be portable as the system will need to be transported to the various contamination sites.
Contaminants frequently present in waste water from a manhole or equipment vault are petroleum products, heavy metals, and a mixture of solids: dirt, leaves, cooking fats, etc. Due to the varying densities of these contaminants, as well as different cohesive and adhesive properties, the liquid in the manholes and equipment vaults will tend to separate into three (3) primary layers if left standing for a sufficiently long period of time.
The petroleum products are found in all three layers as they are present in various forms or states: free, dissolved, and emulsified. The presence of various petroleum states within a single waste water site creates severe problems for clarification as most petroleum removal devices and processes are not designed to remove more than a single petroleum state, which typically is the free oil state. Furthermore, these older designs are ineffective at removing emulsified and dissolved oils which are frequently present within the waste water of manholes and equipment vaults.
The heavy metals, also present in all three layers, are a similarly inconsistent group of contaminants. Varying type and concentrations of the metals renders any remediation method that is metal specific virtually useless.
Solids, typically present in the bottom layer, further complicate the decontamination process as these organic and inorganic materials must be removed before treatment of petroleum products and heavy metals can proceed.